Water is
essential for life. It is required to exchange gases (e.g., oxygen and carbon
dioxide) in respiration, it transports nutrients through the body, it is involved
in most metabolic processes, it dilutes and removes wastes, and it serves as
a coolant. Water is acquired by animals through drinking (free
water), through water in their food (preformed
water), and through water produced as a by-product of metabolizing food
(metabolic water, see respiration).
Water is acquired by plants from the soil using their roots.

produce
uric acid rather than urea -- uric acid requires 10x less water than urea
to rid the same amount of waste.

respiratory
water loss:

stay
in moist microclimate (e.g., burrow); venture out when relative humidity
is high.

nasal water condensation: evaporative cooling
in the nasal passageways cools exhaled air. Because
cooler air holds less water than warmer air, water in the cooled,
exhaled air condenses along the nasal passages. The longer, narrower,
nasal passages found in many desert rodents cools air further and condenses
more water.